Tan Jieyao, Jiang Xingxing, Liu Dongyu, Tang Zhen-Kun, Chulkov Evgueni V, Vasenko Andrey S
Key Laboratory of Micro-Nano Energy Materials and Application Technologies, University of Hunan Province & College of Physics and Electronics Engineering, Hengyang Normal University, Hengyang 421002, China.
HSE University, 101000 Moscow, Russia.
J Phys Chem Lett. 2025 Jul 31;16(30):7659-7665. doi: 10.1021/acs.jpclett.5c01958. Epub 2025 Jul 21.
Two-dimensional (2D) Ruddlesden-Popper (RP) perovskites are considered as promising optoelectronic materials due to their intriguing broadband emission properties. However, the origin of the broadband emission in RP perovskites remains a controversial issue. Herein, we have systematically analyzed the exciton behavior and luminescence properties of 2D (PEA)PbI. Our calculations demonstrate that 2D (PEA)PbI exhibits significant quantum confinement effects, which provide a prerequisite for the formation of self-trapped excitons (STEs). However, the intrinsic STEs are absent in pristine lattices. In contrast, the iodine vacancy (V) is energetically favorable and exhibits a shallow charge transition level above the valence band maximum at ∼2.17 eV, which further induces large lattice deformation around the defect to accommodate STEs. Further excited-state electronic structure calculations strongly suggest that the V-associated extrinsic STEs are responsible for the broadband emission in 2D (PEA)PbI. This mechanistic understanding of exciton properties provides fundamental design principles for high-efficiency light-emitting diodes.
二维（2D）Ruddlesden-Popper（RP）钙钛矿因其引人注目的宽带发射特性而被视为有前途的光电子材料。然而，RP钙钛矿中宽带发射的起源仍然是一个有争议的问题。在此，我们系统地分析了二维（PEA）PbI的激子行为和发光特性。我们的计算表明，二维（PEA）PbI表现出显著的量子限制效应，这为自陷激子（STE）的形成提供了前提条件。然而，原始晶格中不存在本征STE。相比之下，碘空位（V）在能量上是有利的，并且在价带最大值上方约2.17 eV处表现出一个浅电荷跃迁能级，这进一步在缺陷周围诱导了大的晶格变形以容纳STE。进一步的激发态电子结构计算强烈表明，与V相关的非本征STE是二维（PEA）PbI中宽带发射的原因。这种对激子特性的机理理解为高效发光二极管提供了基本的设计原则。
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